A variety of designs of flexural pivots have been proposed for mounting a movable structure (e.g., an oscillating mirror) to a fixed support. Generally, flexural pivots utilize two mounts (e.g., two axially aligned, cylindrical housings) and typically a plurality of flexure members or blades. Each of the flexure members/blades in known flexural pivots are separately and mechanically attached (e.g., via brazing, clamping) to both of the mounts, but are not directly attached to each other. The flexure members/blades allow a limited degree of rotation or pivoting of one mount relative to the other while providing a degree of "torsional-like" resistance to such movements.
The mounts of the flexural pivot interconnect the two desired structures, such as a fixed support and an oscillating mirror. One type of mount which has been utilized for flexural pivots is a pair of substantially cylindrical and axially aligned housings. Generally, each of these housings have a cylindrical end structure with an arcuately-shaped tab (e.g., less than 180.degree. ) projecting from an end of the cylindrical end structure. When assembled, the cylindrical end structures of the two housings are on opposite ends of the flexural pivot and the projecting tabs of the housings extend within the interior of the cylindrical end structure of the other housing. Consequently, when the flexure members/blades are inserted and disposed inside the housings (e.g., via a positioning of the flexure members/blades in preformed slots on the interior of the housings) and appropriately attached thereto (e.g., by brazing), the housings are movably interconnected by the flexure members/blades. Although it has been suggested to separately form each of the housings and each of the flexure members/blades (e.g., U.S. Pat. No. 4,997,123 to Backus et al., issued Mar. 5, 1991), it has also been suggested to form a cylindrical housing by milling a piece stock into the desired cylindrical shape, and thereafter form two housings therefrom by electrochemical or electron discharge and cutting operations (e.g., U.S. Pat. No. 3,807,029 to Troeger, issued Apr. 30, 1974; U.S. Pat. No. 3,813,089 to Troeger, issued May 28, 1974; U.S. Pat. No. 3,825,992 to Troeger, issued Jul. 30, 1974), prior to inserting a flexure member/blade assembly therein for attachment to the housings.
The above-noted types of flexural pivots are deficient in some respects. For instance, manufacturing costs associated with multiple-piece configurations are typically high. Moreover, the assembly of the multiple-piece flexural pivot necessitates the use of some type of mechanical joinder of the flexure members/blades to the mounts. In the case of brazing and the like, these joints are prone to fracture when the flexural pivot is subjected to vibration and shock loading. Furthermore, when brazing it utilized the potential exists for a condition commonly referred to as "bridging". Bridging occurs when the braze material used to join the mounts and flexure members/blades flows into the space between the two mounts and thus prevents independent movement of the mounts.
Many of the above-noted types of flexural pivots, namely those in which the flexure members/blades are not directly attached to each other, also suffer from a "decentering" of the mounts during relative movement between the mounts. Decentering is caused by the lack of a common axis of rotation/pivotation among the flexure members/blades which coincides with the axis of rotation/pivotation of the flexural pivot. Rotation or a pivoting of one mount relative to another mount is again achieved by a bending of the flexure members. Since in the noted configuration the flexure members/blades are not joined along a common axis, the members/blades bend along independent axes. This results in an uneven distribution of stresses among the flexure members/blades which causes a radial translation of one mount relative to the other mount during relative movement of the mounts. In certain applications, decentering adversely affects the precision of the mounted structure (e.g., an oscillating mirror).
Many of the above-noted types of flexural pivots also do not achieve maximum strength from the flexure members/blades. That is, in some configurations the flexure members are separately attached to the mounts only along a portion of the length of the mounts (e.g., to accommodate the assembly of the flexure members/blades prior to positioning such within the cylindrical housings). Strength would be increased if the flexure members/blades extended along the entire length of the mounts and were each attached to the mounts along this entire length. Relatedly, when all of flexure members/blades are not attached to the mounts along their entire length, this necessarily concentrates the stress at the above-noted mechanical joint(s) between the flexure members/blades and the mounts which often results in failure of the joint before failure of the flexure member. Similarly, the attachment of the flexure members/blades along the full length of the mounts and to each other at the centerline would result in higher stiffness in the five axes of motion other than the torsion axis. This would help maintain alignment of the rotating structure under dynamic loads.